Search results for "SILICA"
showing 10 items of 1092 documents
Catalyst activation of silica nano-based pore structure material for hydrogen storage
2011
Silica based composite material with palladium synthesized by extractive-pyrolytic method is used for hydrogen absorption-desorption experiments. The results obtained of the study on dynamic sorption experiments showed that Pyrex glass based composite sample reaches high hydrogen concentration in the material quite fast. Thought silica gel based composite material rapidly reaches 1/2 of hydrogen load but afterwards the amount of hydrogenation increases slowly. The overall amount of absorbed hydrogen for Pyrex glass based material exceeds the amount of absorbed hydrogen by silica gel based material approximately 5.6 times.
Effect of Hydrothermal Treatment on Adsorption Properties of Silica Gel
2011
It has been proven by coupling near infared spectroscopy to second derivative processing of the spectra that the free and hydrogen bonded silanol groups attached to water molecules absorb at 5314 a...
Mechanism of Heavy Element Retention in Hydrated Layers Formed on Leached Silicate Glasses
1988
ABSTRACTWe have investigated the relationship between hydrated layer formation during aqueous corrosion of silicates and retention of heavy elements (Fe, REE, actinides). Our approach is based on the comparison of the dissolution behaviour of silicate glasses, silicate minerals implanted with increasing doses of lead ions (1×E+12 to 1×E+15 ions/cm2), sorption experiments on silica surfaces and direct precipitation of hydrosilicates. The characterization of reacted surfaces was performed by combining Rutherford backscattering spectrometry (RBS) for profiling heavy elements with Resonant Nuclear Reaction Analysis (RNRA) for hydrogen profilimetry. The accumulation of these elements does not ne…
Characterisation and radiolysis of modified lithium orthosilicate pebbles with noble metal impurities
2017
Modified lithium orthosilicate (Li4SiO4) pebbles with additions of titanium dioxide (TiO2) are suggested as an alternative tritium breeding ceramic for the European solid breeder test blanket module. The noble metals – platinum (Pt), gold (Au) and rhodium (Rh), can be introduced into the modified Li4SiO4 pebbles during the melt-based process, due to the corrosion of Pt-Rh and Pt-Au alloy crucible components. In this study, the surface microstructure, chemical and phase composition of the modified Li4SiO4 pebbles with different contents of the noble metals was analysed. The influence of the noble metals on the radiolysis was evaluated after irradiation with accelerated electrons (E = 5 MeV),…
Influence of orthophosphate ions on the dissolution of tricalcium silicate
2008
International audience; Tricalcium silicate dissolution in the presence of orthophosphate ions was monitored by measuring the concentrations of calcium and silicate ions in dilute suspensions using a special dissolution cell coupled to an optical emission spectrometer. Results show that increasing adsorption of orthophosphate ions slows down the dissolution of Ca3SiO5 and that a calcium-phosphate precipitate may form at certain orthophosphate concentrations. These observations are correlated with results of calorimetric experiments carried out during the hydration of silica-rich cement pastes in the presence of the same salts.
Physicochemical properties of Ru(bpy)32+ entrapped in silicate bulks and fiber thin films prepared by the sol–gel method
1999
Silicate porous xerogels doped with ruthenium bipyridine (Ru(bpy)32+) complex have been obtained in the bulk form and in thin films on optical fibers. The hypsochromic shifts in the absorption and emission maxima are accompanied by fourfold increase in the lifetimes of the entrapped complex. The temperature-dependent lifetimes reveal that silicate xerogels induce two competing thermally activated processes in the excited state decay of the immobilized complex. The excited state lifetimes of the doped bulk xerogels and the fibers coated with thin films containing Ru(bpy)32+ are virtually identical to those obtained for the fibers coated with additional gas-impermeable layers.
CVD elaboration and in situ characterization of barium silicate thin films.
2010
International audience; This study is concerned with the elaboration of barium silicate thin films by metal organic chemical vapor deposition (MOCVD) and in situ characterization by X-ray photoemission spectroscopy (XPS) with an apparatus connected to the deposition reactor. The difficulty to find an efficient metal organic precursor for barium is described. After characterizations of the selected reactant, Ba(TMHD)2tetraglyme, the development of an original specific vapor delivering source which allows reactant sublimation in the CVD reactor was performed. In the most optimized cases, including use of oxygen introduction during the deposition, barium silicate films were obtained. Moreover,…
Two new members of the Silica-X family of materials: RUB-5, a silica zeolite with a very high framework density and RUB-6, a hydrous layer silicate
2020
Abstract The new zeolite RUB-5 and the new phyllo silicate RUB-6 were synthesized at temperatures between 130 °C and 200 °C from reaction mixtures consisting of SiO2/LiOH/B(OH)3/OA/H2O or SiO2/KOH/OA/H2O (OA = organic additive). Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and ATR-FTIR spectroscopy confirmed that RUB-5 is a framework silicate while RUB-6 is a layer silicate. The XRD powder patterns were indexed in monoclinic symmetry (space group: C2) with lattice parameters of a0 = 10.2699 (4) A, b0 = 10.6556 (4) A, c0 = 18.1551 (7) A and β = 106.35 (1)° (RUB-5), and a0 = 10.1100 (43) A, b0 = 10.6956 (51) A, c0 = 20.5448 (44) A and β = 105.79 (1)° (RUB…
Raman and IR investigation of silica nanoparticles structure
2013
Abstract In the present investigation we report experimental data regarding the Raman and Infra-Red (IR) absorption activities of commercial silica nanoparticles. We compared the data of the nanoparticles with the ones acquired in the same experimental conditions for commercial bulk silica. By this comparison we highlighted that the variability of the spectral features of the matrix related Raman and IR bands in the nanoparticles is above the one observed for the bulk systems before any treatments. Furthermore, by studying nanoparticles with different sizes (diameters from 40 to 7 nm) and applying the shell-model we can suggest that the core network of the nanoparticles is close to the one …
Ge-doped silica nanoparticles: production and characterisation
2016
Silica nanoparticles were produced from germanosilicate glasses by KrF laser irradiation. The samples were investigated by cathodoluminescence and scanning electron microscopy, providing the presence of nanoparticles with size from tens up to hundreds of nanometers. The emission of the Germanium lone pair center is preserved in the nanoparticles and atomic force microscopy revealed the presence of no spherical particles with a size smaller than ~4 nm. The absorption coefficient enhancement induced by Ge doping is reputed fundamental to facilitate the nanoparticles production. This procedure can be applied to other co-doped silica materials to tune the nanoparticles features.